Increasing cross machine direction extensibility of paper webs



Nov. 30, 1965 F. H. FREULER 3,220,116

INCREASING CROSS MACHINE DIRECTION EXTENSIBILITY OF PAPER WEBS Filed Oct. 2, 1962 2 Sheets-Sheet 1 HIGH AIR PRESSURE FIG. I

INVENTOR FRED H. FREULER BY WW ATTORNEY NOV. 30, 1965 FREULER' 3,220,116

INCREASING CROSS MACHINE DIRECTION EXTENSIBILITY OF PAPER WEBS F I G I 5 IIIIIIIIIIII/IIIIIIIIIIIIIIIIIIIIL FIG.?

INVENTOR FRED H. FREULER ATTORNEY FIG.6

United States Patent 3,220,116 INCREASING CROSS MACHINE DIRECTION EXTENSIBILITY OF PAPER WEBS Fred H. Freuler, Stamford, Conn, assignor to Clupak, Inc., New York, N .Y., a corporation of Delaware Filed Oct. 2, 1962, Ser. No. 227,764 1 Claim. (Cl. 3441) The present invention relates to extensible paper, and more particularly to a method and an apparatus for conditioning a paper web during its manufacture so that the final paper product has substantial and increased extensibility in its cross machine direction.

It is known that a paper web, if permitted to dry free of restrictive forces, will undergo natural contraction and will then have a reversible extensibility approaching the extent of this contraction. The degree of natural contraction which may be expected of a paper web is a function of the type of fiber and inter-action between the fibers within the paper Web during drying, and in the free drying of ordinary kraft paper, for example, can be expected to impart as much as 8-9% extensibility to said paper.

It is an object of the present invention to take advantage of the phenomenon of natural web contraction to produce extensibility in said web, particularly crosswise or in the cross machine direction of the web, by so conditioning the web prior to drying that it is free to contract or shrink in this direction.

Another object is to control the conditioning of the web in relation to the natural capacity of the paper web to contract so that said paper web in its final state has substantially smooth parallel faces and thus is not noticeably different from ordinary paper now produced which does not have substantial cross machine direction extensibility.

Still another object is to condition the web, for the purposes mentioned, using standard and readily commercially available apparatus.

The present invention includes in its scope the provision of a measured amount of looseness crosswise of the web at a point in the manufacture of the paper web just prior to the time that it is confined against drying apparatus which may consist of one or a series of ordinary heating drums. This looseness more particularly might take the form of lengthwise corrugations spaced across the width of the web. Preferably, these lengthwise corrugations are produced in the web by working the web inwardly with a modified so-called Mount Hope roll. It has been found that in the initial stages of drying that a corrugated paper web has only its corrugation crests in surface contact against the heated drum and that the web portions between these crests are therefore not restrained by frictional contact with the drum from freely contracting during drying of the web. Thus, by keeping the looseness added to the web to a value below the maximum ability of the web to contract it is possible to obtain a substantially smooth surfaced final product with greatly enhanced cross machine direction extensibility because of the substantial contraction of the web in this direction.

Various other objects and advantages will appear from the following description of one embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

FIG. 1 is a side view of apparatus for conditioning a paper web prior to drying in accordance with the present invention;

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FIG. 2 is a side view of a paper web drying apparatus;

FIG. 3 is a plan view projected from FIG. 1 with the air hood 16 removed;

FIG. 4 is a view, partly in section, similar to FIG. 3 but with the paper web P removed; and

FIGS. 5, 6 and 7 are illustrative of the condition of the paper web, prior to, during, and after drying thereof, respectively.

In FIGURES 1, 3 and 4 is shown a'so-called Mount Hope roll 10 of the type which is commercially available in a variety of sizes from the Mount Hope Machinery Co. of Tauuton, Mass. Structurewise, roll 10 has a stationary bowed steel shaft 11 on which is rotatively mounted a series of side-by-side ball bearing units 12. Attached to the units 12 is a cylindrical rubber cover 13. Thus, there is produced a continuous stretching and contraction in the rubber cover 13 as this cover changes from a convex -to a concave curvature during rotation about the bowed shaft 11. A very common use for the Mount Hope roll 10 in the paper making art is to remove wrinkles from a paper web, said Web being fed onto the roll at the point in its rotation just prior to expansion of the rubber cover '13,.

In accordance with the present invention, however, the roll 10 is utilized to produce a reduction in width of the paper web, and more particularly to form a pattern of lengthwise corrugations adjacently spaced across the width ofthe web which then constitutes a measured amount of looseness crosswise in the web. For this purpose, and as most clearly shown in FIG. 4, the rubber cover 13 of the roll 10 is preferably provided with a series of circumferential grooves 14 across its width. The grooves :14- provide a discontinuous surface to the cover 13 which aids in inducing the paper web .P to partake of the contraction of the cover, but other surface patterns and techniques to accomplish this objective are of course also possible. As shown in FIGS. 1 and 2 the paper web P is fed onto the rubber cover 13 at the point in its rotation about the shaft 11 where it changes from a convex to a concave curvature. A preferred technique for adhering the paper web P to the contracting rubber cover 13 so that it is corrugated by the contraction of the cover 13 is to direct high pressure air against the paper web P through a hood 16. In lieu of high pressure air, however, other techniques may also be employed to adhere the web to the cover 13. For example a soft bristle brush may be used to hold the paper web P against the contracting cover 13 and for some machines the usual lengthwise tension or draw on the paper web may be adequate to achieve this desired result.

Thus, the effect of the mechanical working or conditioning which is produced by the action of the modified Mount Hope roll 10 in the paper web P is to work the paper Web inwardly forming therein a pattern of smoothly curved corrugations 17 across the Width of the web P, as is best illustrated in FIG. 5. Further, in accordance with the present invention the corrugations 17 that are provided in the web P are related to the expected natural shrinkage of the web so that in its final state the paper Web is completely devoid of any corrugations 17, and as regards surface smoothness, is not noticeably different from paper now produced which ordinarily is prevented by frictional contact against the heated dryer drum from contracting movements along the drum surface and thus does not have substantial cross machine direction extensibility. This is accomplished by reducing the width of the web P an amount up to but not exceeding the natural capacity of the web to contract crosswise. Thus with a web 240 inches wide and having a natural capacity to contract 8%, in any one pass or number of passes over a corrugating roll 10 the total web width reduction should not be permitted to exceed approximately 19 inches.

After being modified to the condition illustrated in FIG. 5, the paper web P is fed into a conventional drying apparatus which may consist of a series of identical heated drums, such as the drums designated 18 in FIG. 2. As shown in FIG. 2 an endless moisture-permeable felt belt 19 mounted on rollers 21 and onto and around the rotating heated drums 18 carries the paper web P against the drum during drying. In the ordinary case Where a fiat paper web is confined by the felt belt 19 against the surfaces 22 of the drums 18, the surface friction which exists between the drum surface and moist paper web is sulficient to resist and prevent contraction, either lengthwise or crosswise, in the paper web. However, when the paper 'web is provided with lengthwise corrugations 17 the web portions 17a between the corrugation crests 17b are free of contact with the drum surface 22 as is most clearly shown in FIG. 6. In this regard, the frictional adherance of the web at the spaced corrugation crests 17b is sufficient to maintain and support the web in its corrugated condition against the light pressure exerted on the web portions 17a by the felt 19 so there is no pressing or flat tening down of the web portions 17a, and these web portions, during web drying, are therefore free to shrink or contract. This contraction is more particularly only crosswise of the Web since the web is still under lengthwise tension which of necessity must be maintained on the web to move it lengthwise over the heated drum. It will further be understood that ideally the paper web P as it leaves the dryer drums will have substantially 'smooth parallel faces 23 and 24 as is illustrated in FIG.

7 and thus is not noticeably different from paper produced which has not been modified with corrugations 17 prior to drying. Yet the final paper product of the present invention will have enhanced cross machine direction extensibility due to natural shrinkage or contraction in this direction.

The roll 10 of FIG. 4 is of a commercially available type'which has the proper dimensions particularly suitable for conditioning a kraft paper web prior to drying. More particularly, an illustrative roll 10 will be understood to have a width W of 240 inches corresponding to the paper machine wire width, a diameter D of 10.5 inches, and a bow B of 6 inches which is the maximum bow that it has been found feasible to use in an on line installation of this width. Limited to a bow of 6 inches, the roll 10 is therefore capable of producing approximately only a .87% reduction in widthin the paper web P in each pass over the roll. This is of no consequence, however, since several rolls similar to roll 10 may be placed in series to provide any overall reduction in width of the paper P that is desired, or alternatively an appropriate number of passes may be made over the roll 10.

The following are several tabulations of laboratory runs of samples of paper web conditioned with lengthwise corrugations 17 prior to drying thereof compared with control samples (not conditioned) which serves to point out the substantial enhancement of cross machine direction extensibility in the final paper product which is obtainable,

Percent Cross Machine Data Direction Extensibility Run 1:

Test #1 3. 4 Single roll-Groove size: 1/16 inch Control #1. 2. 8 deep. Basis weight: 40#/3,000 ft. Test #2 3. 7 Paper speed: 10.3 ft./n1in. paper Control #2- 3. 1 width: 12"}(6 inches. Test #3 3. 5 Percent contraction of roll: 2%. Control #3. 3.1 Diameter of roll: 3 inches. Dryer temperature: 230 F. Run 2:

Test #1 5. 1 Two rools in sequence- Groovesizcs: Control #1- 3. 3 24g) inch deep (A); 962 inch deep Test #2 4. 1 Basis weight: 40#/3,000 it. Paper Control #2- 2. 9 width: 12 inches. Test #3 3. 9 Diameter of rolls: (A) 3 inches, (B) 6 Control #3 3. 4 inches, percent contraction of rolls:

( and 5%.

It will be understood that various changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claim.

What is claimed is:

In'the formation of a paper web traveling in the machine direction during which the web is to be dried by passing same in surface contact with a heated metallic surface, the improved method of drying the web to obtain a substantially smooth surfaced product with substantial extensibility in a direction crosswise to the direction of web travel, which improved method includes reducing the web in width and creating a measured amount of looseness crosswise of the web by passing said Web in rolling contact with a roller having a flexible, grooved outer surface that is curved along its axial length so that the web becomes progressively smaller in dimension in the direction of web travel due to the progressive contact with the curvature in the flexible, grooved surface in order to sequentially gather said web in the direction crosswise to the direction of travel of the web to form lengthwise corrugations spaced across the width of the web and then passing the web in contact with a heated surface and thereby, drying said web in order to provide a substantially smooth surfaced web with enhanced crosswise extensibility and the faces of said Web being confined during a portion of the drying cycle.

References Cited by the Examiner UNITED STATES PATENTS 1,787,520 1/1931 Hampel 3441 1,908,406 5/1933 Clem 34-116 1,975,708 10/1934 Bleibler 34--41 2,207,122 7/ 1940 Hayward 34-41 2,245,014 6/1941 Sherman 1621 17 2,633,430 3/1953 Kellgren et al. 161l28 2,825,117 3/1958 Evans et a1. 2618.6 3,104,197 9/1963 Back et al. 162180 PERCY L. PATRICK, Primary Examiner.

N RMA Y DKO xam ner, 

